Tank construction



April 19, 1960 c. DOBELL 2,932,964

TANK CONSTRUCTION dri inal Filed'Sept. 14; 1954 2 Sheets-Sheet 1 INVENTOR. Curzon Dobell A TTOR/VEY April 19, 1960 c. DOBELL 2,932,954

TANK CONSTRUCTION Original Filed Sept. 14, 1954 2 sheets-Sheet 2 Fig 4.

INVENTOR.

Curzon Dobell dzwmg x 1! TTORNEI Unit State Pate TANK 0NSTRUCTION Originai application September 14,

456,037. Divided and 1955, Serial No. 542,717

3 Claims. (c1. 72 1s 1954, Serial No. this application October 25,

This invention relates to methods for the construction of concrete tanks and more particularly relates to an improved method of prestrcssing such tanks.

This invention is particularly directed toward reducing the restraint to which the side walls of such tanks are subjected especially at or near the top and/or bottom of such wall.

'In prestressing tanks, the side walls are subject to con siderable inward movement due first to the setting of the concrete but more importantly due to the wrapping of high tensile strength reinforcement around the wall to prestress it.

In prior techniques, care has been given to free the lower portion of the wall so that it might move inwardly, a typical method being shown in U.S. Patent 2,433,652. The top portion of the wall has usually been rigidly locked to the roof, usually by heavy reinforcing, so that there was considerable restraint acting on the top of the wall. These came either from the expansion or contracting of the roof or due to the varying liquid levels in the tank, which might at times vary from a high maximum to a low zero. To. overcome these forces heavy vertical reinforcing, usually prestressed was required to counteract the bending moments caused by such restraint which might otherwise cause the walls to crack.

It is therefore an object of this invention to eliminate as much as possible the restraint acting on the sidewalls of a concrete roofed tank. It is a further object to provide aconcrete tank in which the sides, roof, and base are free to move relatively independently of each other without sacrificing liquid tightness at the junction of these components. It is a further object to provide means for positively providinga water barrier inthe case the footing and the side wall separate from each other. It is yet a further object to provide all of the above while nevertheless protecting the tank against earthquake and other shock that might cause the wall to move on its base or the roof on the wall. Theserand other objects will appear as this specification proceeds.

This invention proposes to have the concrete sidewalls of a tank attached at both the top and bottom to the dome and base respecively, firstly by resilient means permitting freedom of movement laterally and also secondly, by a further resilient means permitting independent vertical movement without loss of liquid seal. This invention further proposes to provide a chamfered key between side walls and base in combination with the above.

An understanding of both the details and the principles of this invention may best be had by an immediate reference to the drawings which illustrate the preferred mode of application of the principles of this invention and to the following detailed description of this mode of application of this invention.

In the drawings, Figure 1 is a partial sectional elevation of a domed tank showing the sidewall construction.

Figure 2 shows an enlarged, cross-sectional view of r the method of connecting the sidewall to the base.

Figure 3 shows a cross-sectional view of a chamfered key base and sidewall before prestressing.

Figure 4 shows the final position of the chamfered ey sidewall after prestressing.

Figure 5 is a sectional elevation showing the resilient means at the top of the tank.

More particularly in the drawings, the tank 2t} comprises base 22 resting on subsoil 28, sidewalls 24and roof 2d. The sidewalls 24 are completely freed from rigid contact with both the dome and the base by the use of a resilient pad 32, preferably of rubber of low durometer such as 40, at the top and bottom of the sidewall. To retain the liquid seal, dumbbell 30 is used also at the top and bottom. If the base or footing should settle in any one, sector, as occasionally occurs despite the most elaborate precautions, then the dumbbell 30, being locked in position, retains the seal and prevents the resilient pad 32 from being dislodged by the internal liquid pressure.

The base 22 as shown in this figure is constructed with a high outer sector and a low inner sector in order to provide as much volume as possible within the tank.

The sidewalls 24 have narrow-mouthed receptacles 34 built into the wall during construction. Into these receptacles are placed the prestressing wires 36 after which they are covered with grout.

The steps in construction of the tank sidewall are shown in Figure 2. In this figure the base 22 is poured and into it is inserted the dumbbell 3i After the concrete has set, rubber pad 32 is laid in place and then a level base is built up on each side of the pad 32 to provide a more or less level bottom surface edge for the sidewall. An inexpensive material usually available at most sites is clay which is roughly shaped as shown in builtup sections 38 and 40 and covered with paper separator 42. Formwork 44 is built up and the upper end of dumbbell 30 is attached by wire 46 to rod 48 at intervals. The dumbbell must be continuous and sealed at the joints. The rubber pad 32 must be continuous but need not be sealed. The wall 24is then poured in place. It has been found that a resilient pad the full width of the wall produces too much restraint. The pad must be as narrow as possible consistent with supporting the superimposed dead load, hence the need for a filler each side.

After the concrete of the wall has set, the clay is flushed out, or in some instances may be left in place depending on the wishes of the constructor. The wall is then subjectedto prestressing by any of the conventional methods, the one shown in the drawings being that using internal channels or receptacles for holding prestressing wires. When the concrete of the wall sets there is a slight inward movement of the wall due to shrinkage, but the greater movement is due to the prestress. The final position of the wall is shown in Figure 4. The above description is that of the deformation of the resilient pad at the bottom of the sidewall.

Figures 3 and 4 show another modification of base and sidewall using the resilient pad-dumbbell combination of this invention. In these embodiments an even greater internal volume is possible than in the embodiment shown in Figure 1. In these figures, the base 22 is provided with an elevated peripheral step 5%. The dumbbell 13b is anchored in place when the base is poured. When hardened, the resilient pad 132 is mounted in place as shown. it must be of sufficient thickness so that when compressed there will be ample clearance between the wall and the base, and such that the maximum expected movement of the base and wall does not distort it through an angle change of over 70. It must be of sufiicient width that the loading on the pad caused by the wall and its overburden will not cause compressive stress of Patented Apr..19 taco 3 more than 500 psi.v In practice ina thirty foot diameter tank, the step or key 50 is about inch in height, and the pad 132 is inch in thickness. Using forty durometer rubber, the clearance will be A inch after the wall is poured.

Clay (not shown) is now placed on top of the step-5i to a level equal to the top of the pad but: is placed on the base 122 inside the dumbbell only to the top of its hollow bulb. When the wall is poured the overlapping protrusion 52 will be'formed. This overlap between 50 and 52 provides a convenient key to assure that the tank will stay on its' footings during earthquakes, etc. The key is also valuableto keep the tank in position when the tank is .backfilled unevenly Iand movement occurs.

Figure {shows the condition after prestressing. The clay is washed out and pres'tressing is accomplished. The wall 124 will then have moved inwardly to, a position as shown. I

Figure '5 shows the 'use of a copper waterstop 2250 as a substitute for the resilient rubber waterstop shown in the'remai'ning figures.

Figure 6 shows a detail for constructing the joint at the top of the wall when a dome is used The sidewall 24 is formed with a peripheral 'lip 62 and hold-down bolts 64 are set in place. The dome 26 is then poured. Bonding of the bolts 64 to the concrete of the dome is prevented by coating the bolts with a heavy bituminous cover and then further covering them with a pipe sleeve 66, the inside of which has alsobeen heavily coated u'ith a bituminous cover. The protrusion 60 on the dome is made in the same manner as at the base of the wall.-

The pad-dumbbell combination at the top as well as the base of" the wall, together with the keyway overlap of dome and sidewall provide a useful prestressed construc tion to resist shock, earthquake, hurricane, etc.

- This application is a division of my copending application Serial No. 456,037, filed September 14, 1954 and now abandoned.

section attached to the second section and sufficiently embedded in the base to prevent detachment therefrom, and resilient means of width substantially less than the width of the sidewall and under compression between osages 7 movement between the wall and the base, and a third 7 the sidewall and the base to separate one from physical contact with the other and to permit predetermined movement.

2. A concrete structure according to claim 1, char:

acteriz'ed thereby in that the said first and third sections of the connector are provided wtih a deformation in each section to maintain it in an embedded condition.

3. A concrete structure for containingjfluids comprising a base,'an endless prestressed sidewall having a lower surface, said lower surface defining an inner edge with the inner surface of the side wall and an outer edge 7 with the outer surface of the sidewall, resilient pad means disposed between said lower surface of the side wall and the upper adjacent surface of'the base, said resilient pad means being under compression and spacing the side wall from the base and yet permitting predetermined movement therebetween, said pad means being of a width substantially less than the width ofthe side wall, the pad means being spaced inwardly of said outer edge of the side wall and being spaced outwardly of said inner edge of the side wall, and an endless elastic connector, said connector including three sections, .a first section being embedded in said base tolprevent detachmenttherefrom, a second section bridging the space between said side wall and the base and'b eing of sufiicient strength to withstand the maximum'hydraulic pressure to which it may be subjected and yet being .sufficientlyflexible to accommodate the =maximurn degree of movement between the side wall and the base, a third section of the connector being'embedded in the sidewall and projecting through the lower surface of the side wall lying between the inner edge of the side wall and the pad means. V

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Journal of the American Concrete Institute, vol. 27, No. 1, September 1955, page 85.

7 ,Great Britain of 1950 

